[SOLVED] 
My problem with Roboform was fixed by installing the latest Roboform adapter. I just directly logged in to this forum using Roboform after reinstalling WB 7. All I did was select Stardock Forums from the "Logins" drop down box in the Roboform toolbar.
It turns out that Firefox updates do NOT update the Roboform extension, even if you click Tools -> addons -> Extensions in Firefox, then click "Find Updates". You have to click the Options button under Roboform in the Extensions window, then select "Version" in the Roboform popup window, then click "Check New Version...". If the new Roboform browser window/tab reports a more recent version of Roboform than you see when you select "Adapter" in the Roboform popup window, you should download the latest version to your HD and install it. I personally chose to first uninstall the current Roboform extension from Firefox.
Note that you can have an older version of the Roboform Adapter in Firefox than the version reported by your Roboform system tray icon. I did and that's what threw me. You've got to check the Roboform version in Firefox separately. Bad design on Roboform's part, I think.
I hope this post helps other people who have problems with the Roboform toolbar in Firefox.
Anyway, if I can determine that WB 7 is usable for me at 120dpi, I'll buy it. Checking it out now.